Method of rendering wool unshrinkable and non-felting



United States Patent@ METHOD OF RENDERING WOOL UNSHRINKABLE AND N ON-FE'LTING Menachem Levin, Jerusalem, Israel, assiguor to The Ministry of Agriculture (The Institute for Fibres and Forest Products), Jerusalem, Israel, a ministry of the Government of Israel No Drawing. Application January 4, 1956 1 Serial No. 557,243

both unshrinkable and non-felting, as contrasted to known processes which render the wool merely unshrinkable.

The terms unshrinkable or shrinkpoof denote the property of the wool to resist washing shrinkage, while non-felting or feltproof" mean resistant to severe milling treatment, both the washing shrinkage and. felting being expressed in term of area shrinkage.

It has already been proposed to render wool unshrinkable by treatment with an aqueous liquor containing hydrochloride acid and a water-soluble bromate. process is described, for example, in the'British patent specification No. 614,271 and the U.S. patent specification No. 2,508,007. It was based on the observation that when wool is immersed in an aqueous bromate-HCl-solution, a certain amount of chloride and bromate anions are sorbed by the wool and can ultimately be retrived by ample washing with water, while .the amount of HCl and bromate contained in the treating liquor above the sorbable proportion produces the shrinkproofing. The earlier process takes as a measure for. the successful shrinkproofing, the disappearance of bromate ion from the liquor in the amoutn of 6.5 to 16 grams per kilogram.

of air-dry wool, without distinction between merely sorbed bromate and bromate reduced, ile. consumed irretrievably. If the directions given by the specifications aforesaid are followed it is found that very roughly onehalf of the quantity of bromate disappearing from the liquor is sorbed, and one half is reduced.

Wool shrinkproofed by the earlier process aforesaid.

It is now found that when.

desirable because the process, when performed on a corn-. mercial scale, becomes too much protracted, and unless, the sorbed bromate is thoroughly removed from the wool,;

which again is apt to be a costly operation, it is liable to damage the fibers in storage and in subsequent handling. The invention, therefore, sets out so to improve the earlier process that complete shrinkproofing and feltproofing of the wool can be obtained in an operation of relatively short duration with a of damage to the fiber.

Accordingly, the invention consists in a process of rendering wool shrinkproof and feltproof by immersion in an aqueous acid bromate solution, wherein the solution contains bromate ions in an amount of 1.45 to 6.25%, an alkali or alkaline-earth chloride in an amount of from 20 to 120% (calculated as chloride ion), and a This it lCe strong mineral acid in an amount at least equivalent to the bromate, all percentages being by weight of the airdry wool; and the wool is left immersed in the solution for the time required for the disappearance from the solution of bromate ion in the amount of about 1.3 to 2.1% by weight of air-dry wool.

It is found that under these conditions, the bromate disappearing from the solution is almost wholly lost irretrievably by reduction, while the proportion of re trievably sorbed bromate ion hardly reaches and vitually never exceeds 0.4% of the air-dry wool so that out of the total proportion of bromate disappearing, about 1.3 to 1.7% is lost irretrievably.

The proportion of chloride added to the solution is a controlling factor for the time required for the treatment at any given temperature as well as for the proportion of retrievably sorbed bromate; the higher the chloride proportion under otherwise equal conditions, the shorter is the necessary time of immersion for a given temperature, or the lower is the required temperature for a given time of immersion and the lower is the proportion of sorbed bromate.

Moreover, the addition of the chloride makes possible the use of somewhat less acid and less bromate than in the known process referred to above.

The chloride may be, for example, that of sodium,

' potassium, magnesium or calcium.

As mineral acid one may use, for example, hydrochloric, sulfuric or perchloric acid. Its proportions will have to be at least equivalent to the bromate. Suitable concentrations of hydrochloric acid are, for example, of the order of 0.05 to 0.3 N (acidity of the bath as a whole), and of sulfuric or perchloric acid of the order of 0.05 to 0.5 N.

It has been found that wool treated by the process according to the present invention does not change its outward appearance, feel, microscopic features (i.e. the scales are not damaged), dry and wet strength, abrasion resistance, whereas the alkali solubility, the frictional properties and the 30% reduction-in-work-index are only slightly changed to an extent which does not show any damage done to the fiber. There is also no loss in the Weight of the wool though it.has been found that the treatment brings about a reduction in the cystine content of the wool by about 10-13% of its original amount.

The invention is illustrated by the following examples, all percentages given being by weight of air-dry wool:

Example 1 1.14 kg. of air-dry wool cloth (containing 14% of moisture) was immersed in an aqueous bath. of 26 liters having the temperature of 25 C. and containing per liter 3.55 grams of HCl (0.097), 2.1 grams of potassium bromate corresponding to 1.6 gram of bromate ion, 14.6 grams (0.25 mole per liter) of sodium chloride, and 0.12 gram of an acid resistant wetting agent, e.g. Tergitol 7 (trademark). After about 72 minutes the wool was removed from the bath, rinsed thoroughly in water and in an aqueous solution of 0.15 gram of sodium thiosulfate per liter, and again in water. The amount of bromate ion retrievably sorbed was 19.3 millimoles, corresponding to 2.48 grams of bromate ion per kilogram of air-dry wool. The amount reduced was about 114 millimoles of bromate ion, or 14.7 grams of bromate ion per kilogram of air-dry wool.

The washing shrinkage and milling shrinkage (felting) of the wool were determined according to the usual methods: the washing-shrinkage test was performed by treating sample patterns of the wool cloth in 0.5% soap solution for 1 hour at C. in the W.I.R.A. washwheel. The milling shrinkage test as a measure of the non-feltability consisted essentially in vigorous handmilling for 15 minutes in 1% soap solution at 40 C., or in mechanical milling for 1 hour in a 1% soap solution at 40 C. in a suitable fulling machine. While the area shrinkage of the original and untreated wool-was in the-washing shrinkage test 24.6% and in the milling shrinkagetest 38.3%, it was reduced in the wool treated according to Example 1 to nil in washing shrinkage, and to about 0.2 to 2% of area shrinkage, in the milling test.

Example 2 The composition of the liquor was the same as in Example 1, except that the proportion of sodium chloride was 29.2 grams (0.5 mole) per liter, and'the' time of immersion was about 45 minutes. Thea'mount of .bromate ion reduced and the non-felting properties were the same as in Example 1. The amount of sorbed bromate was 13 millimoles, or slightly below 1.7 gram per kilogram of air-dry wool.

Example 3 Example 4 1.14 kg. of air-dry wool (containing 14% of moisture) was immersed in 26 liters of an aqueous bath having the temperature of 25 C. and containing per liter 2.45 grams of hydrogen chloride (0.069 N), 0.77 gram 0.006 mole) of bromate ion corresponding to 1 gram of potassium bromate, 59.5 grams of sodium chloride (1 mole per liter) and 0.2 gram of sodium lauryl sulfate. The time of immersion was about 155 minutes. The amount of sorbed bromate ion was 3.50 millimole corresponding to 0.44 gram per kilogram of air-dry wool. The amount of reduced bromate was 123 millimoles, corresponding to 15.8 grams per kilogram of air-dry wool. The shrinking and felting properties of the treated wool were the same as in Example 1.

Example 5 1.14 kg. of air-dry wool (containing 14% of moisture) was immersed in an aqueous bath of 26 liters having the temperature of 15 C. and containing per liter 3.55 grams of HCl (0.097 N), 0.77 gram (0.006 mole) of bromate ion corresponding to 1 gram of potassium bromate, 73 grams of sodium chloride (1.25 mole per liter) and 0.2 gram of Tergitol 7 (trademark) as a wetting agent. The time of immersion was about 105 minutes. The amount of sorbed bromate ion was 2.6 millimoles, corresponding to less than 0.33 gram per kilogram of air-dry wool. The amount of reduced bromate ion was 127 millimoles corresponding to 17 grams per kilogram of air-dry wool. The after-treatment and the shrinking and felting properties were the same as in Example 1.

Example 6 35 kg. of air-dry Wool yarn was immersed in a Pegg dyeing machine containing 1000 liters'of a solution having the temperature of 2425 C. and containing per liter 6 grams of HCl (0.165 N), 0.54 gram (0.0055 mole) of bromate ion corresponding to 0.7 gram of potassium bromate, and 50 grams of sodium chloride (0.86 mole per liter). The solution was circulated through the yarn for about 70 minutes.

After that time the wool was rinsed with water, then with an aqueous solution containing 0.1 gram of sodium thiosulfate per liter, and-again with water. The amount of sorbed bromate ion was 3.7 millimoles corresponding to 0.48 gram per kilogram of air dry wool. The amount of reduced bromateion was 113 millirnoles corresponding to 14.5 grams 'per kilogram of air-dry wool.

The shrinking and felting'properties were the same as in Example 1.

Example 7 34 kg. of all-wool socks was immersed in a paddle-type dyeing machine containing 1000 liters of a solution having the temperature of 24-25 C. and containing per liter 8.5 grams of sulfuric acid (0.173'N),'0.54 gram (0.0055 mole) of bromate ion corresponding to 0.7 gram of potassium bromate (2% of the weight of the air-dry socks) and 50 grams'of sodium chloride (0.86 mole per liter).

The time of treatment was 150 minutes. The aftertreatment, the amounts of bromate ion sorbed and reduced and the non-felting properties were the same as in Example 6.

What I claim is:

l. A process for rendering wool shrinkproof and feltproof comprising immersing the wool in an aqueous acidbromate solution containing bromate ions in an amount of 1.45 to 6.25% and a substance from the group consisting of alkali and alkaline-earth chlorides in an amount of from 20 to 120% (calculated as. chloride ion), and a strong mineral acid in an amount at least equivalent to that of the bromate, all percentages being .by. weight of air-dry wool; and leaving the wool immersed inthe solution for the time required for the disappearance from the solution of bromate ion in an amount of about 1.3 to 2.1% by weight of the air-dry wool, the irretrievable bromate ion being from 1.3 to 1.7 percent and the retrievable sorbed bromate ions being from 0 to 0.4 percent.

2. A process as claimed in claim 1, wherein the solution is acidulatedwith a mineral acid selected from the group consisting of hydrochloric, sulfuric and perchloric acids to such an extent that the acidity of the solution is of the order of 0.05 to 0.3 N.

3. A process as claimed in claim 2, wherein the solution is acidulated with hydrochloric acid to an acidity of 0.05 to 0.3 N.

4. A process as claimed in claim 2, wherein the solution is acidulated with sulfuric acid to an acidity of 0.05 to 0.5 N.

5. A process as claimed in claim 2, wherein the solution is acidulated with perchloric acid to an acidity of 0.05 to 0.5 N.

References Cited in the file of this patent UNITED STATES PATENTS Barnes July 26, 1955 .OTHER REFERENCES General Method of Making Wool Shrink-Resistant, by R. W. Moncrietf; The Textile Manufacturer, October 1950, pp. 502-505.

Trotman Jan. 13, 1925 

1. A PROCESS FOR RENDERING WOOL SHRINKPROOF AND FELTPROOF COMPRISING IMMERSING THE WOOL IN AN AQUEOUS ACIDBROMATE SOLUTION CONTAINING BROMATE IONS IN AN AMOUNT OF 1.45 TO 6.25% AND A SUBSTANCE FROM THE GROUP CONSISTING OF ALKALI AND ALKALINE-EARTH CHLORIDES IN AN AMOUNT OF FROM 20 TO 120% (CALCULATED AS CHLORIDE ION), AND A STRONG MINERAL ACID IN AN AMOUNT AT LEAST EQUIVALENT TO THAT OF THE BROMATE, ALL PERCENTAGES BEING BY WEIGHT OF AIR-DRY WOOL, AND LEAVING THE WOOL IMMERSED IN THE SOLUTION FOR THE TIME REQUIRED FOR THE DISAPPEARANCE FROM THE SOLUTION OF BROMATE ION IN AN AMOUNT OF ABOUT 1.3 TO 2.1% BY WEIGHT OF THE AIR-DRY WOOL, THE IRRETRIEVABLE BROMATE IONS BEING FROM 1.3 TO 1.7 PERCENT AND THE RETRIEVABLE SORBED BROMATE IONS BEING FROM 0 TO 0.4 PERCENT. 